When children reach adolescence and young adulthood, they become dramatically less active. Efforts to increase physical activity among adolescents and young adults (15-25 years old, henceforth summarized as youth) face two challenges. First, physical activity recommendations that promote cardiovascular health for youth stem from relatively little data in this population. Second, interventions designed to increase physical activity in youth have produced at best modest and mixed results. Behavioral economics is a promising field for designing incentive interventions to promote healthy behaviors for cardiovascular health. Behavioral economic interventions may be especially potent in youth. This is because developmentally youth have stronger reactions to reward and peer influence. The research objective of this K application is to develop a behavioral economic intervention to increase physical activity in youth. I will intentionally design an intervention for youth in three ways. First, I will analyze data from >3500 youth in the National Health and Nutrition Examination Survey to determine the amount of physical activity associated with improved cardiovascular health in youth. Second, I will elicit youth preferences on physical activity, financial incentives (e.g., gain- or loss-framed), and social incentives (e.g., methods for selecting and communicating with team members) through a discrete choice experiment with 400 low-income youth. Finally, I will design a financial and social incentive intervention using a youth-centered, participatory approach. The incentive intervention will be piloted in a 2-month feasibility trial with low-income youth. The intervention will leverage insights from Positive Youth Development theory to maximize the impact of behavioral economic interventions in low-income youth. I will capitalize on resources at Duke University, where I am an Assistant Professor of Pediatrics and a faculty member of the Duke Clinical Research Institute, Duke-Margolis Center for Health Policy, and Duke Center for Childhood Obesity Research. The current application will provide a structured environment with expert mentorship to enable me to develop as an independent investigator and future leader in behavioral economic interventions to promote cardiovascular health in youth. I will complete a career development plan comprised of formal didactic training in the epidemiology of health behaviors for cardiovascular health, mixed methods research techniques, patient- centered research, and the conduct of behavioral economic intervention trials. I have assembled a mentorship team with extensive expertise in these topics and a history of successful mentorship of junior faculty. I have included a young adult advocate as an advisor, whose youth perspective will help guide my research. This work and training will inform my investigator-initiated research proposals for R01 trials to test the efficacy of behavioral economic incentives to increase physical activity in adolescents and young adults. Insights from this work will also be applicable to a range of other youth health behaviors for cardiovascular health, such as those related to smoking, healthy diet choices, and medication adherence.